The difference is the DSO will store one single record, possibly for Eternity. The DPO will make a compromise with Eternity, storing the more recent traces bright and the more older ones, gradually fainting. In this way, if you have a steady signal with short transients un-synchronized with it, you will catch a glimpse of the transients and you will be able to synchronize with the transients, or use single-shot to get them. Also, in a lot of noise, you will have the opportunity to see what's the signal you are synchronized on, because that one will be brighter. If you can understand these things you will find great comfort and use for the phosphorescence (or persistance). It helps "unblock" you many times. "Phosphorescence" is just a romantic term for "persistance" stemming from the most available material having this property, Phosphor. The idea is the beam of electrons hits the Phosphorus, and the Phosphorus emits light after that, fainting slowly over time. This effect can easily be implemented in software. Tektronix made a big fuss about introducing the effect using a specialized chip. Well, far from mocking Tektronix, but the "specialized chip" thing is a joke. The real thing Tektronix did was to realize the need and the use for this kind of display. Probably some old experienced engineers insisted on doing it, and the PR from Tektronix insisted it must be a "specialized chip". The "specialized chip" is a joke, any Pentium 120MHz can implement digital Phosphorus well enough. I've seen it in 1999 🙂 However, the "digital Phosphor" effect can be extended a lot using digital processing. This is no longer a limitation of chips. They can do anything you want, only if you make up your mind. From the simple exponential decaying curve of the original Phosphor, to any combination of colors and decaying speeds you can think of, and even waveform recognition and highlighting. All you have to do is ask, preferably in good LabVIEW 🙂 You can ask anything from a computer in LabVIEW 🙂
